Welcome to Mayo Clinic podcast. Our topic today is breast MRI, specialized screening for breast cancer. I'm your host, Rich Dietman.

Mammography is considered the standard screening test for breast cancer, but in early 2007 an expert panel of the American Cancer Society recommended annual breast cancer screening with magnetic resonance imaging, or breast MRI, in addition to mammography for women at high risk of breast cancer. This is the first time that breast cancer screening guidelines have included breast MRI. Today we're talking with Dr. Sandhya Pruthi, a breast-health specialist at Mayo Clinic, about what this change in screening guidelines means. Dr. Pruthi, thanks for being with us.

Dr. Sandhya Pruthi: Thank you.

Rich Dietman: Dr. Pruthi, start by explaining what the difference is between a screening mammogram and a screening breast MRI.

Dr. Sandhya Pruthi: A mammogram is actually radiation. It's an X-ray, much like you would go in for a chest X-ray. So it's the radiation that you're getting with the use of mammography; whereas MRI is a magnetic energy, and with sound waves — radio waves — the images come out in a computer-generated two and three dimensional-type imaging that helps the radiologist see and interpret that imaging, which is very different from mammography.

Rich Dietman: So you get two different pictures?

Dr. Sandhya Pruthi: Very different pictures, with different types of technology.

Rich Dietman: What are the current screening guidelines for mammography?

Dr. Sandhya Pruthi: Most people would follow the American Cancer Society guidelines, which recommend that women, beginning age 40, should have annual mammograms. However, there are other organizations that have different recommendations. And that's kind of been some of the issues in the United States — with some beginning at age 50 with annual mammography; some organizations say every other year, beginning age 50. But in general, most are following beginning at age 40, annually.

Rich Dietman: What's significant about the breast MRI being added to the American Cancer Society's screening guidelines, and what factors influenced their inclusion?

Dr. Sandhya Pruthi: We have to remember now, that the American Cancer guidelines were specific for high-risk women — very high-risk women — and their addition of their guidelines on the use of MRI were specific to this group, not to your general population. So those factors that came into why the American Cancer Society brought these guidelines forward this year was that there were increasing data and studies showing that in high-risk women the use of MRI had a better detection or sensitivity in picking up cancers, compared to mammography in that group. And the numbers that are quoted is that mammography has a greater sensitivity in a high-risk group of about 30 percent, whereas MRI is as high as 70 to 80 percent.

Rich Dietman: So MRI is actually better at detecting breast cancer?

Dr. Sandhya Pruthi: It certainly can have a better detection in, again, a high-risk group, not your general risk.

Rich Dietman: So why do women in high-risk groups need to get both a mammogram and the MRI?

Dr. Sandhya Pruthi: Mammography actually is very good in picking up micro-calcifications that could be an early sign. Especially if they're irregular or multiple or clustered — that could be an early sign of a cancer. And one common description of a cancer is a ductal carcinoma in situ, and MRI still hasn't reached that technology, and may in the next few years, but as of today that technology — the MRI — may miss those microcalcifications. So in essence they're complementary. You really want both. You can't replace a mammogram with an MRI today in a screening situation.

Rich Dietman: What are some of the risks and limitations of breast MRI? And talk a little bit also about false-positive tests.

Dr. Sandhya Pruthi: There are several risks to having an MRI, and I'll outline them for you. And then I want to spend a little more time talking about the false-positives. The risk that I would like a patient to be aware of before they go through an MRI is that it does require an intravenous contrast injection of a dye called gadolinium, and that may have a very slight risk of an allergic reaction. So that is something women need to know about. The other risks of an MRI are that you could end up going on to have an MRI-guided biopsy — which could, in essence, be a harmful technique because it's an invasive procedure — for something that is seen on an MRI. Some limitations of an MRI are that the timing of the MRI should be done before you ovulate and after you menstruate. So that week of the timing of the MRI — especially for premenopausal women — is important. And by doing it in the correct time period of their menstrual cycle, you're less likely to pick up some of these enhancements, or false-positives. So let's talk about false-positives. By that I mean an MRI could detect a lesion, a low-suspicion lesion — or an enhancement is what they say — and the radiologist recommends that this be further evaluated. By that, they would ask that you may have another ultrasound to look at that area more closely and then recommend a biopsy. And if the biopsy goes on to become benign, or noncancerous, in essence you've got a false-positive here. And that happens up to 20 to 30 percent of the time in a woman who goes through an MRI. So it's higher than we like, and actually higher than what we see with mammography.

Rich Dietman: And this could be an anxious period of time …

Dr. Sandhya Pruthi: Definitely. And so overall, just all of this that MRI can lead to with the risks and limitations creates a general anxiety for some women, and frightening for some women as well.

Rich Dietman: And that's part of the anxiety part too you're talking about.

Dr. Sandhya Pruthi: Exactly. And I think that women need to know that this isn't going to be a single, simple test. There may be additional tests down the line. And it certainly has made women more anxious.

Rich Dietman: So who should get a breast MRI?

Dr. Sandhya Pruthi: That's a great question. And I think what's really frustrating for primary care providers and women is defining who's high risk and what definition do we really use. There really isn't a textbook definition for "high-risk"; there are certain factors that we would look at. To define a woman at high risk today is if she carries the BRCA1 or 2 gene mutation, which infers up to a 40 to 80 percent lifetime risk of getting breast cancer. If she has a very strong predisposition to carrying the mutation because of a family history where there are multiple relatives — not just one, but multiple who are diagnosed with breast or ovarian cancer before age 50, young-onset cancers, — and if there was a male relative with breast cancer or a relative who had a first-degree relative who had cancer in both breasts, these are risk factors that a geneticist takes into account to determine if this woman may be at predisposition to carrying a mutation. She may choose not to, but they could assume, using models, that this is a very high-risk individual. A woman whose received radiation to her chest wall before age 30, for a treatment of Hodgkin's lymphoma, a very common treatment, is at high risk for breast cancer — up to a 30, 40 percent lifetime risk. And then there's another criterion that the American Cancer Society put out there, and they used the term greater than 20 to 25 percent lifetime risk. And that really put a lot of, I think, physicians into a quandary as to how do you get to that number. And really, you can only get to that number by specific models, models that are available that allow you to enter the age of onset of a relative and the number of relatives, and then with that you can get a calculation. So it's not just simply that somebody walks into my office today and says, "My mother had breast cancer at 80." She may be her first-degree relative, but the onset, a single relative, is not going to put her at high risk. So that group we would not be screening with breast MRI.

Rich Dietman: So if a woman does come to you and is determined by these criteria to be at high risk, what do you recommend?

Dr. Sandhya Pruthi: I certainly would talk to them about the new guidelines and review with them the risks and the limitations and the benefits of MRI, and that it is a complementary study to mammography, not in addition. And today the guidelines are saying that these women should be screened with both tools annually. That again is a recommendation, and I think you really have to individualize it based on your patient and the characteristics and her anxiety.

Rich Dietman: Does insurance typically cover breast MRI?

Dr. Sandhya Pruthi: I think if you qualified as a high-risk individual based on the criteria I reviewed, the insurance companies are taking that into account and are covering the test. But I really emphasize to my patients that they need to talk with their insurance company — that my doctor's considering an MRI, based on this criteria — and make sure that that is covered. Otherwise, it is a test that runs close to $4,000.

Rich Dietman: So it could be quite an expense, a personal expense.

Dr. Sandhya Pruthi: Right. And then the additional biopsies that could come with that and the additional MRIs that follow.

Rich Dietman: What about women who aren't at high risk, who don't fit one or more of those criteria, but have very dense breast tissue? Doesn't MRI do a better job of screening than mammography for dense breast tissue?

Dr. Sandhya Pruthi: That's a good question. And what I like to come back to is sort of the basics on what do I mean by dense breast tissue in this one specific case, which a large number of women have. And most women who are premenopausal, who are still menstruating, will have very dense breast tissue, just by the context of the hormonal impact on the breast during those years. And so density is the proportion of fat to connective tissue in the breast tissue. And that's what creates sometimes the problem for mammography — the proportion of connective tissue is so much more than the fat, which makes the mammogram dense, therefore harder to interpret. But if we were to offer every woman who has dense breast tissue — which is a large percent of premenopausal women — MRI, there's no way we could screen. Plus it's not been looked at in that context — as a tool that has been shown to have the ability to (screen for cancer in dense breasts) and (to be) cost effective. So, no. I would not offer a breast MRI today to a woman with dense breast tissue by just that factor alone. If she has other risk factors, then I would want to take into account and individualize it. For example, if she has had precancerous changes or she has a family history; if she's had a personal history, and maybe the cancer was not detected on the mammogram initially when she was diagnosed with breast cancer, we may factor those into the decision-making process. But again, it's very individualized and I would not — and further the American Cancer Society has not shown the evidence that supports for or against screening in this group of women who have had dense breast tissue or precancerous changes. So it does make for a difficult decision-making process for many of us and again, factoring in the cost and the anxiety of this test.

Rich Dietman: Thanks very much, Dr. Pruthi. We've been talking with Dr. Sandhya Pruthi, a breast-health specialist at Mayo Clinic. You've been listening to Mayo Clinic podcast. I'm Rich Dietman.

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